OK, devils advocate strikes again. In essence what Adair is saying is absolutely true on all things covered. However; many techniques are species specific and will not translate to other species well. So; you have to research what it is you want to do and do it. It is my understanding that the Japanese are known to spiral wire around a trunk and allow it to be over-grown, forcing the tree to grow over it and adapt. It is my understanding that this is a technique used on Japanese Black Pine if it is used at all and you will not encounter it in every source you look into. To the beginner this stuff sounds wonderful and a welcome short cut to fat trunks and so forth. The truth is if you do not know or understand what you are doing this could be disastrous leaving you with wasted time and a dead tree. It is true that the quickest way to accomplish what you desire is to plant the tree in the ground. With Junipers this is the easiest way, and with Pines this will produce fat trunks but the bark will not be so good. So-- no matter what you do it depends on your knowledge, experience and skill----not to mention a degree of luck.
The little Mugo shown below (8" tall) is the product of this accidentally and by neglect happening quite a number of years ago. You cannot now see the wire but much of it is still present. You decide.
The truth is, there is no substitute for trees that already posses large trunks, even if the tree is five foot tall and the bonsai your desire is only two feet tall. This is of course the secret of growing bonsai from nursery trees. The only two alternitives are Yamadori which are expensive, difficult to maintain, and impossible to acquire without permits and other hoops to jump through. The only other alternitive is to purchase pre-bonsai from a professional grower that will be glad to charge you the cost of a Chevrolet. This is of course takes us back to your original post. Grow it your self. Do your self a favor; start with larger trees not pencils and straws, start with nursery trees with substantial trunks. The secret is to cut down a nursery tree into a smaller bonsai. The Mugo below starter in a one gallon container it is not about 7-8"s tall. This kind of reduction can be done much quicker than trying to grow a stick into a quality bonsai.
View attachment 246196